1. Field of the Invention
The present invention as disclosed in the first and second embodiments relates to a two-wheel drive two-wheeled vehicle, and more particularly a two-wheel drive motorcycle having the rear wheel driven by the traditional chain or shaft mechanism and the front wheel driven by a series of shafts and gears transferring power to the front wheel from either the motorcycle transmission or the driven rear wheel. Moreover, as a novel and inventive improvement to all prior attempts at constructing two-wheel drive motorcycles and two-wheel drive bicycles including the embodiments disclosed in related applications, the two-wheel drive motorcycle disclosed herein is configured so that the front wheel drive components counterbalance all steering system torque reactions and moments of inertia through placement of numerous components located on the axis of steering and symmetrically within the motorcycle front fork. The novel configuration enable the rider to maintain control of the two-wheel drive motorcycle during the high-speed, high-power rotation of the engine-powered front wheel drive.
2. Description of the Related Art
As motorcycle and off-road motocross riding has gained broader appeal, the demands that riders place on their vehicles have increased dramatically. Conventional motorcycles are powered through a chain or shaft linking the engine to the rear wheel. However, motocross and motorcycle riders are now facing riding conditions and obstacles where having only rear wheel drive can lead to vehicle damage, loss of control and an unstable front wheel during cornering and off-road riding in general. For professional riders, precious race time is lost avoiding obstacles or losing traction in loose rocks, sand, dirt, mud, or ice. Traction and climbing ability are severely limited in extreme mountain conditions by only having the rear wheel provide power. Accordingly, there is a need in the industry for a two-wheel drive motorcycle that efficiently and safely transfers power from the motor through the transmission to the front wheel, that provides the rider with increased ability to safely negotiate rough terrain, and that does not detract from the aesthetic qualities, appearance or function of the motorcycle itself.
While both two-wheel drive motorcycles and two-wheel drive bicycles have been attempted in the past, the present invention relating to the two-wheel drive motorcycle offers significant technical and functional innovations previously not disclosed or anticipated. The present invention features symmetrically positioned and counterbalanced front wheel drive components relative to the axis of steering and motorcycle centerline that eliminate or minimize the torque reactions that would otherwise adversely affect motorcycle control when the front wheel is driven. Additionally, the present invention illustrates a front wheel drive for a two-wheel drive motorcycle that is completely enclosed within the motorcycle frame, head tube, and front fork in a way that reduces danger to the rider from moving parts and ensures that the motorcycle steering is unencumbered.
By comparison, previous attempts at constructing a two-wheel drive motorcycle have utilized hydraulic, hydrostatic, and variations of belt, shaft or chain drives that have numerous exposed parts. Importantly, none of the previous attempts at constructing a two-wheel drive motorcycle would result in a functional two-wheel drive motorcycle. Primarily, none of the prior attempts have taken into account that a motorcycle drive system based upon rigid shafts can spin at several thousand revolutions per minute producing torque reactions along the front fork from the spinning front wheel drive system that would result in an uncontrollable pull on the front wheel. Furthermore, previous attempts have failed to provide a motorcycle with a full rage of steering.
U.S. Pat. No. 4,702,340 shows a motorcycle with a front wheel driven by a chain supported by the motorcycle fork and handlebars powering a large chain drive gear on the front wheel. The patent is assigned to Rokon International who previously produced a similar two-wheeled vehicle capable of only low-speed rough terrain maneuvering. As shown, the front wheel drive chain would severely limit the ability to manufacture a motorcycle capable or any high speed maneuvering.
U.S. Pat. Nos. 5,014,808, 5,050,699, 5,054,572, and 5,113,964 show variations of motorcycles with a front wheel powered by a series of belts, chains, gears, or sprockets from the motor to the front fork and then to the front wheel along one side of the fork. While a motorcycle does not need the same broad range of steering that is necessary for a bicycle, the presence of a bulky drive chain on one side of the motorcycle would cause problems with both steering as well as unwanted torque reactions that would make the motorcycle potentially uncontrollable at high speeds. The exposed front wheel drive chains also pose a potential hazard to the rider.
U.S. Pat. Nos. 5,873,428 and 5,894,903, JP9156570A2, EP 0 779 205 A2, and EP 0 779 205 A3 show motorcycles with a front wheel driven by hydraulic motors or hydrostatic pressure from the engine to the front wheel. A motorcycle with a front wheel driven by a hydraulic drive system would have significantly less efficient power transfer than a rigid-shaft drive system.
GB Patent Number 1,284,821 shows a motorcycle with a front wheel driven by an extremely complex shaft and gear drive system. The motorcycle includes a radically-redesigned front end without a head tube, very large gears extending well in front of the axis of steering, and a front drive system located within one fork leg. The adverse torque reactions resulting from the unbalanced front wheel drive system and high-speed rotation of the front wheel drive would likely result in a motorcycle that is uncontrollable. This configuration of the front wheel drive would also prevent a full range of steering.
WO 93/09992 (PCT/FR92/01084) discloses a front wheel drive for a two-wheel drive motorcycle that is not counterbalanced on the axis of steering and is located in a significantly enlarged front end lacking a head tube. Such a front end would interfere with the full steering range of the motorcycle during sharp turns and make the motorcycle impossible to ride on complex terrain and potentially pose a safety risk. Additionally, while the invention discloses a drive system within both fork legs, the invention fails to disclose a counter-balanced drive system as several gears are vertically offset from each other. Further, as illustrated, the dimensions of a standard motorcycle would require that the drive gears be several inches in diameter and both the shafts and gears are inadequately supported for the enormous torque that would be transferred through such a drive system design. In short, the disclosed two wheel drive vehicle fails to adequately address the problem of torque counter balancing or provide a full range of steering.
The attempts at constructing two-wheel drive two-wheeled vehicles also include several two-wheel drive bicycle designs. Generally, two-wheel drive bicycles fall into two categories: 1) permanent designs involving drive trains attached to the frame, and 2) retrofit kits which convert existing bicycles to two-wheel drive. The main drawbacks to these systems are: 1) a modification to the standard bicycle in the form of a kit is expensive when considered as an addition to a bicycle purchase, 2) the low strength flexible shaft limits the allowable loading on the system, 3) the retro-fit kit requires considerable skill to attach and cannot be designed to optimally work with every frame design, and 4) the drive mechanisms are often large and openly exposed on the outside of the frame potentially creating additional hazards for the rider and detracting from the overall appearance of the bicycle. In short, none of the two-wheel drive bicycles discussed below could be successfully modified or adapted to produce a functional two-wheel drive motorcycle.
U.S. Pat. No. 4,773,662 shows a bicycle with a front wheel driven by a chain connected to a handlebar mounted hand pedaling system. The bicycle uses arm power to drive the front wheels and is adaptable to a conventional bicycle frame.
U.S. Pat. No. 5,542,689 shows a front wheel drive system for a bicycle which can be installed on a bicycle to drive the front wheel by rocking the handlebars back and forth. As with U.S. Pat. No. 4,773,662 mentioned previously, this bicycle attempts to harness the energy of the rider""s arms as an additional power source for driving the bicycle. However, a drive mechanism requiring the use of the riders arms for more than steering, balance and control of the vehicle would likely create safety problems and interfere with the bicycle""s operation for both professional and recreational mountain bikers.
U.S. Pat. No. 5,052,705 describes a bicycle with power distribution from the rear wheel to the front wheel via a caliper and cable drive system. The drive system is activated by a caliper clamped on the rear wheel connected by a cable to a caliper on the front wheel. Inefficient power transfer to the front wheel due to slippage as well as torque loss in the cable would likely be a problem with this system.
U.S. Pat. No. 5,224,725 describes one permanent system that has been developed utilizing a series of chains and sprockets. This design utilizes many moving parts that would make the bicycle very awkward and difficult to maintain. The exposed chain that runs along the top tube could be hazardous to the rider and the front chain also would interfere with steering.
U.S. Pat. No. 5,324,057 describes a bicycle driven with a chain meshed with both the front and rear sprockets through a plurality of gears, pulleys and spring systems to power the front wheel.
U.S. Pat. Nos. 5,332,244, 5,253,889, 5,158,314, 5,116,070, and 4,895,385 disclose two-wheel drive bicycles including a front wheel driven by flexible cables or flexible cables in combination with chains. Other systems, such as the system produced by Turner Drive Systems of Rogers, Ark., target the market for a drive system which can be retrofit to any standard bicycle frame with modifications primarily to the gearing and chain attachments necessary to drive the front wheel. As discussed above, a cable-driven front wheel results in inefficient power transfer to the front wheel due to cable wind.
U.S. Pat. No. 5,332,244 discloses chain-sprocket arrangements, along with a flexible shaft to transmit some of the power from a rear gearbox. to the front wheel. The retrofit system utilizes the inner most sprocket for the drive system, however the rider can use the other sprockets to shift gears normally. Deformation of the flexible cable, and corresponding loss of efficient power transfer from the rear wheel to the front wheel is a drawback of each of these systems when compared to the rigid shaft drive of the present invention.
U.S. Pat. No. 5,158,314 uses a complex mechanical system to power the front wheel from the powered rear wheel. A first traction chain coupled to the rear wheel and attached to the frame is connected to a series of rigid and flexible shafts which attach to a second traction chain which is mounted above and powers the front wheel. U.S. Pat. Nos. 4,029,332 and 4,474,660 also describe two-wheel drive bicycles with complex chain or belt drive and pulley systems.
Bicycle hubs utilizing roller clutch bearings are described in U.S. Pat. Nos. 5,485,905 and 5,662,197. However, neither application discloses the use of the roller clutch hub to provide power transmission advantages for the front wheel drive of a two-wheel drive bicycle nor does either utilize more than a single roller clutch within the hub for added strength and durability of the hub shell.
As a point of reference and comparison, the family of applications related to the present invention focuses primarily on embodiments, related to two-wheel drive bicycles, that are functionally and technically different from the novel aspects of the two-wheel drive motorcycle disclosed herein. While the embodiments relating to the two-wheel drive bicycle disclosed a fully-functional two-wheel drive bicycle, the same design could not be utilized with and would not result in a functional two-wheel drive motorcycle. Primarily, the fact that the bicycle front wheel drive is located in only one fork tube would make the two-wheel drive motorcycle uncontrollable in normal riding conditions due to unbalanced torque reactions which would tend to pull the steering mechanism in one direction the slower rotation of the human-powered drive system of the two-wheel drive bicycle makes it unnecessary to counterbalance the torque reactions that are produced by placing the drive system within only one fork tube. Thus, while the single drive shaft within the front fork of the two-wheel drive bicycle is important for minimizing weight in the bicycle, such a concern is less important for the engine-powered motorcycle. Additionally, the fact that the drive system is located in only one fork tube would make the two-wheel drive motorcycle uncontrollable in normal riding. The high-speed, engine powered rotation of the front wheel drive makes counterbalancing, minimizing and canceling the torque reactions, essential to the proper functioning of the two-wheel drive motorcycle.
The disclosed embodiments of the two-wheel drive motorcycle are novel and inventive over all prior two-wheel drive motorcycles and two-wheel drive bicycle attempts. The two-wheel drive motorcycle disclosed herein is configured so that the front wheel drive components counterbalance all steering system torque reactions and moments of inertia. Furthermore, the two-wheel drive motorcycle of the present invention includes numerous components located on the axis of steering within the head tube. The two-wheel drive motorcycle disclosed herein features paired components, gears, and drive shafts positioned symmetrically relative to the centerline and axis of steering (in a mirror-like fashion) within the motorcycle lower crown and front fork. The two-wheel drive motorcycle of the present invention has a full-range of uninterrupted steering enabling the rider to maintain control of the steering of the two-wheel drive motorcycle during the high-speed rotation of the engine-powered front wheel drive.
The two-wheel drive motorcycle of the present invention includes a head tube that encloses a front wheel drive and includes a separated neck tube that supports the front fork and steering mechanism on bearings within the head tube to enable rotation of the steering mechanism around the front wheel drive gears.
The two-wheel drive motorcycle of the present invention includes a rigid shaft front wheel drive supported by bearings and, therefore, does not experience the inefficient power transfer to the front wheel of other previously-disclosed front wheel drive systems.
The two-wheel drive motorcycle disclosed herein further includes a rigid front wheel drive that powers the front and rear wheels instantaneously, without power loss, and in a ratio which enables safe and effective operation of the motorcycle and provides instantaneous transfer of power from the motor to the front wheel.
The two-wheel drive motorcycle of the present invention further includes a motorcycle frame and front fork that substantially enclose the front wheel drive within the head tube and fork of the motorcycle providing effective power transfer to the front wheel with no interference of rider motion, with normal braking and steering radius, and with minimal rider danger from moving parts.
The two-wheel drive motorcycle disclosed herein further includes a front wheel drive that may be adapted to a variety of common motorcycle frame configurations and designs including motocross, enduro, road and touring motorcycles.
The two-wheel drive motorcycle of the present invention further optionally includes an engagement clutch in the front wheel drive that allows the rider the option to choose between rear-wheel-only drive, two-wheel drive, or front-wheel-only drive operation when conditions warrant.
The front wheel drive technology of the present invention may optionally be incorporated into a shock-absorbing front fork and rear suspension system of a motorcycle to provide the rider with a smoother ride.
The two-wheel drive motorcycle disclosed herein also optionally includes a free wheeling front hub that utilizes a roller clutch bearing, or any other type of ratcheting clutch, or sprag clutch bearing. Additionally, in one alternative embodiment, the free wheeling hub includes a torque-limiting clutch to prevent failure of the front wheel drive under extreme torque loads.
The two-wheel drive motorcycle disclosed herein further proposes alternative drive systems that can be incorporated into the frame, head tube and front fork of the motorcycle or within tubing attached to the frame to power the front wheel either from the rear wheel or directly from the engine and transmission in the center of the motorcycle. One such alternative front wheel drive features a ball-bearing drive system.
Other features and advantages will be more fully apparent from the following disclosure and appended claims.
The present invention is a two-wheel drive motorcycle, otherwise known as an all wheel drive motorcycle or a motorcycle powered by both the rear and the front wheels simultaneously. The two-wheel drive motorcycle disclosed herein may include a shock-absorbing front fork or rear suspension system. Additionally, the front wheel drive of the two-wheel drive motorcycle may be adapted to a number of motorcycle frame configurations including motocross, enduro, road, cruising and touring motorcycles.
The present invention, as specifically described in the first and second embodiments, has several novel and innovative features when compared to all previously attempted two-wheel drive motorcycles and bicycles, including the two-wheel drive bicycle disclosed in related applications. First, the two-wheel drive motorcycle disclosed herein is configured so that the front wheel drive components counterbalance steering system torque reactions and moments of inertia. Second, the two-wheel drive motorcycle disclosed herein includes numerous components located on the axis of steering within the head tube to minimize or negate any torque reactions that could negatively affect steering and control as power is transferred to the front wheel.
The two-wheel drive motorcycle disclosed herein features paired or counterbalancing and symmetrical components, gears, and drive shafts positioned relative to the axis of steering and centerline within the motorcycle lower crown and front fork to minimize or negate torque reactions that could negatively affect steering and control as power is transferred to the front wheel. The two-wheel drive motorcycle configured with symmetrical drive shafts and components in the front fork and head tube as disclosed herein facilitates a full-range of uninterrupted steering while enabling the rider to maintain control during the high-speed rotation of the engine-powered front wheel drive.
Unlike the previously disclosed two-wheel drive bicycles and motorcycles, this invention discloses a front wheel drive for a two-wheel drive motorcycle that includes components and at least two front wheel drive gears located on the steering axis within the motorcycle head tube. Additionally, the two-wheel drive motorcycle disclosed herein optionally incorporates the front wheel drive within the head tube and a neck tube that is severed, or features a cut-away section. However, any front wheel drive that contains components along the axis of steering either within the head tube or in the vicinity of where a typical head tube would be located between the fork members is contemplated by the present invention.
Additionally, it is desirable to place the rotating front wheel drive components along the steering axis above the front wheel so that there is limited tendency to produce rotational torque to the front wheel during normal and high-speed operation. Moving the front wheel drive components even a small amount off the steering axis could result in torque reactions that would make steering difficult. Furthermore, placing the drive components symmetrically along each side of the front fork, thus, rotating in opposite directions, provides a counterbalancing effect to offset the torque reactions. The front wheel drive configuration of the present invention provides stability to the motorcycle and enables steering and operation at all speeds.
Additional features of the two-wheel drive motorcycle disclosed herein include a front wheel drive that transfers power to the front wheel from gears originating within the motorcycle""s transmission of from gears located at the rear wheel. The front wheel drive may include rigid shafts and meshing gears or a number of other drive components and assemblies, including ball bearing drives, that are internalized within the motorcycle frame and that minimize power loss when powering the front wheel without limitation of the steering range. A two-wheel drive motorcycle in accordance with the present invention provides a rider with increased safety and the ability to significantly increase speed during navigation through dangerous stretches of terrain.
The two-wheeled drive motorcycle of the present invention further uses a series of rigid shafts as the main power transfer means to the front wheel. Rigid shafts have the advantage of virtually instantaneous power transfer, whereas flexible shafts usually have from 10 to 20 degrees of rotational displacement when subject to a torque which would lead to a spongy feeling. Similarly, hydraulic drives are not as efficient as a rigid drive system in transferring power through the system. Additionally, a rigid shaft drive is supported by bearings which results in very low friction in the front wheel drive system.
The front wheel drive system of the two-wheel drive motorcycle of the present invention is substantially enclosed either within the frame or within tubing attached to the frame, within the head and neck tubes, and/or within the front fork crown and fork tubes to maintain the front wheel drive in a fixed position thereby minimizing or eliminating slippage and, as importantly, enclosing the moving parts to minimize danger to the rider. Enclosing the front wheel drive system will also maintain the general aesthetic appearance of the motorcycle. Prior two-wheel drive motorcycles and bicycles features numerous external drive chains to the front wheel that significantly detracted from the appearance. Enclosing the front wheel drive within the head and neck tubes and modifying the neck tube to accommodate the front wheel drive while turning enables the motorcycle steering mechanism to turn smoothly without interference with the front wheel drive system. Finally, enclosing the front wheel drive facilitates adaptation to numerous common motorcycle frame designs including motocross, road, and touring.
The front wheel hub of the two-wheel drive motorcycle of the present invention is design to attach meshing gears. More specifically, the power is transferred to the front wheel from the motorcycle""s transmission or rear wheel through a rigid drive system that includes gears located on the lower end of the symmetrically-position drive shafts located within each fork tube that mesh with gears mounted on either side of the front wheel hub. The gears may feature either straight or helical (spiral) gear teeth although helical gears are preferred for strength, smoothness and quieter power transfer.
The head and neck tube or the steering axis region of the motorcycle of the present invention are modified to accommodate at least three meshing gears with one being attached to the front end of the main drive shaft that originates at the motorcycle""s transmission or from the rear wheel and the other two being attached to drive shafts which attach to gears located within the lower fork crown. The meshing gears are supported on bearings within the head tube to keep the bearings and front wheel drive components aligned along the steering axis. The disclosed configuration further provides an optimum fork angle relative to the ground for steering responsivenes and control without restricting steering of the two-wheel drive motorcycle. The head and neck tubes, which may be either standard sized or enlarged, are modified so that the neck tube will not interfere with the meshing front wheel drive gears while the motorcycle is being steered.
The neck tube of the two-wheel drive motorcycle of the present invention is preferably cut away in the center to accommodate the meshing gears that are supported on bearings within the head tube to keep the bearings and front wheel drive components aligned along the steering axis. More specifically, the neck tube is cut away or severed to create two separate sections of neck tube above and below the rotating front wheel drive gears and components within the head tube. The neck tube sections are then supported by needle bearings within the head tube and by clamping power of the fork crowns above and below the head tube. In that way, the head tube acts as a gear casing located between the upper ends of the fork members and below the handlebars. It is important that the casing be positioned so as not to interfere with rotation of the handlebars and fork members.
The front wheel drive shafts descending within the front fork posts of the two-wheel drive motorcycle and free rotation of the front tire as well as to create no interference with the disk brake system. In the first and second embodiments disclosed herein, two series of symmetrical meshing gears within the fork crown transfer power outward from the axis of steering to the drive shafts located within the fork members on each side of the front wheel. Alternatively, a universal joint system could be utilized.
The front wheel drive system of the two-wheel drive motorcycle of the present invention also may include an adjustable component to enable the compression of the front fork and may also include an adjustable component to accommodate movement of the rear suspension if the front wheel drive originates at the rear wheel. As in the first embodiment, sliding shafts within the fork tubes could be utilized to accommodate the expansion and contraction of the shock-absorbing front fork. Alternatively, a telescoping universal joint could be utilized to adjust for lengthening and shortening of the front fork. Also, numerous alternate drive gear combinations can be used instead of the miter gears for transmitting power from the main drive shaft to the front drive shaft system.
The front wheel drive system of the present invention optionally includes an engagement clutch located either within the motorcycle""s transmission or at the rear wheel to enable the rider to optionally shift the two-wheel drive motorcycle from rear-wheel-only drive to two-wheel drive to, potentially, front wheel only drive if the clutch is located within the transmission. The engagement clutch for the front wheel drive could be either a hydrostatic or hydraulic clutch as is well know in the industry or a cable-activated mechanical clutch featuring engaging dog tooth plates as shown in the fourth embodiment of the present invention.
A free wheeling or one-way front hub utilizing at least one roller clutch is also disclosed. The roller clutch has the advantage of being virtually instantaneous in engaging as the one-way hub reverses from its free-wheeling direction to the engaged direction. The free wheeling hub disclosed herein may also feature a torque limiting clutch to prevent front wheel drive failure upon the transfer of severe torque loads through the drive system.
Thus, according to the broad aspects of the invention, the two-wheel drive motorcycle of the present invention may include:
(a) a rigid front wheel drive that transmits power from the engine and transmission or from the rear wheel to the front wheel, through a series of rigid drive shafts including a main drive shaft and a front drive shaft and a series of meshing gears or, alternatively, through other front wheel drive configurations such as a ball bearing drive system that would provide similar efficient and instantaneous power transfer to the front wheel;
(b) a frame, head tube, steering tube, and front fork constructed of tubing, including sections which enclose the front wheel drive system;
(c) a front wheel drive with components that i) are located on or very near the steering axis and preferably, within the head tube and neck tube that have been modified to accommodate the front wheel drive as it rotates, ii) are designed to minimize torque reactions due to the rotating shafts, and iii) are designed to accommodate a full range of steering;
(d) a pair of front drive shafts positioned symmetrically relative to the centerline and a pair of front drive shafts located on opposite sides of the front wheel to counterbalance rotational torque reactions from the front wheel drive and also configured to enable both free motion in the steering of the motorcycle and free rotation of the front wheel without interfering with braking or tire rotation;
(e) a front wheel drive with an adjustable component to accommodate the movement of a shock-absorbing front fork or a rear suspension to ensure a smoother ride;
(f) an engagement clutch to provide the rider the option of shifting the motorcycle from two-wheel drive to rear wheel-only drive;
(g) a one-way hub in the front wheel resulting in minimal backlash to enable virtually instantaneous power transfer to the front wheel;
(h) a torque-limiting clutch to enable release of extreme torque loads within the front wheel drive prior to failure.
In summary, in the present invention, the power is transferred from the engine of the two-wheel drive motorcycle through a rigid front wheel drive that includes a series of meshing gears. The frame of the motorcycle is designed to contain the front wheel drive system that transmits power to the front wheel.
The power is transmitted from the engine to a front wheel drive shaft that originates either within the transmission or from the rear wheel. A drive gear at the front end of the main drive shaft meshes with at least one additional drive gear that is located at or very near the axis of steering and along the centerline within the head and steering tube. Additional front wheel drive components along the axis of steering cancel or minimize the effect or torque generated from the spinning front wheel drive on the rider""s ability to control and steer the two-wheel drive motorcycle. Additionally, the neck and head tube are standard-size or, alternatively, enlarged in comparison to a standard bicycle to allow for full steering capabilities while transferring power to the front wheel. The paired rigid front wheel drive then descends symmetrically along both sides of the front wheel through either a series of meshing gears that may be located within the fork crown, or alternatively with a universal joint to attach to the front wheel drive shafts. Those skilled in the art will recognize other methods for constructing a front drive shaft system that does not interfere with the front wheel, and the embodiments disclosed herein are not to be construed as limiting.
The front drive shafts transmit power through shafts along both sides of the front wheel within the front fork through the meshing of drive gears attached to the lower end of each front shaft and gears mounted circumferentially on each end of the front wheel hub. The front wheel hub may be a one-way hub that catches in one direction but freewheels in the other direction to enable the rider to coast freely. The front wheel hub could utilize at least one roller clutch to enable one-way freewheeling. Roller clutches have the added advantage of silent operation and nearly instantaneous engagement. While virtually all ratcheting hubs feature some degree of backlash as the ratchet engages, the roller clutch engages virtually as soon as the rotational direction of the hub changes. This feature is important for the front wheel drive so that any power transferred through the front wheel drive will result in instantaneous front wheel traction whereas the use of a ratcheting front hub would result in some degree of rotational backlash in the front hub before the front wheel would engage and become powered by the front wheel drive. Additionally, the use of more than one roller clutch within the front hub would provide additional strength in the system by spreading the torque forces over a larger surface within the hub shell.
As disclosed, the front wheel drive system of the present invention may be completely incorporated into a shock-absorbing front fork of the two-wheel drive motorcycle. The sliding front drive shafts slide within the meshing gears or, alternatively, an inner sliding shaft and an outer sliding shaft within the fork member slide relative to each other with the change in length of the shock-absorbing front fork. Alternative front fork designs include the use of expanding ball spline universal joints in the place of the meshing gears. The complete integration of the front wheel drive within the front fork crown and fork members is important for both aesthetic appearances of the motorcycle as well as minimizing danger to the rider from exposed rotating parts. Additionally, the enclosure of the front wheel drive within the fork tubes keeps the front wheel drive in a fixed position to increase efficiency of power transfer. Those skilled in the art will recognize other methods for constructing and mounting a shock-absorbing front fork onto the motorcycle""s frame in a manner which does not interfere with steering or rotation of the front wheel while enabling the front drive shaft system to expand and to contract with the expansion and contraction of the shock-absorbing front fork.
One embodiment of the two-wheel drive motorcycle of the present invention features power transfer directly from the engine and transmission to the front wheel through a rigid drive system. The rigid drive system is internal to the motorcycle frame or within tubing attached to the motorcycle frame and within the head tube and steering tube to enable a full range of steering and instantaneous power transfer to the front wheel. Furthermore, in contrast to two-wheel drive bicycles previously disclosed, front wheel drive components located symmetrically relative to the axis of steering and centerline are important for controlling torque reactions while steering or operating the two-wheel drive motorcycle.
Similar to a two-wheel drive bicycle, the two-wheel drive motorcycle has increased traction and mobility of the front wheel, especially during uphill climbs and downhill cornering on loose or slippery material. A shock-absorbing front fork and rear suspension ensures a smoother ride and greater contact of the front wheel with the terrain for all-around improved rider experience. The invention discloses a method of manufacturing a functional two-wheel drive two-wheeled vehicle with all the disclosed embodiments.